We have demonstrated that neoantigens appear in human IgG after it has bound antigen. This was shown by raising antibodies in rabbits which reacted with antigen bound, but not monomeric or nonspecifically aggregated IgG. We have extended these studies to the development of monoclonal antibodies against human IgG in mice tolerized with monomeric or nonspecifically aggregated IgG. We have made several different monoclonal antibodies. Some recognized antigen bound IgG and plate bound monomeric IgG equally well. Some recognize monomeric IgG better than antigen bound IgG. We also have one antibody which recognizes antigen bound IgG better than monomeric plate bound IgG. We have developed new flourescent methods for the study of pneumococcal phagocytosis which allow us to separate the adherence phase and the ingestion phase of hagocytosis. Using this assay we have examined the nature of the receptors through which human monocytes and PMN adhere to bacteria and the receptors through which they ingest the adhered bacteria. We also have described rate constants for each of these reactions.